Thermal head

Abstract

A thermal head is provided with a heat accumulating member disposed on a substrate, a plurality of heating resistors juxtaposed on the heat accumulating member in a manner to be spaced from each other, electrodes for supplying electric power to the heating resistors, and a protective member for preventing oxidation and wear of the heating resistors and the electrodes, these constituents being formed as layers. When the electric power is supplied to the electrodes, heat is generated by a heating portion of the heating resistor corresponding to the electrodes, and it is transmitted to a head surface via a thermally conductive member disposed in a printing dot portion of the protective member. The heat from the printing dot portion is used for effecting printing on a medium to-be-recorded through a thermosensitive sheet which lies in contact with the head surface.

We claim: 
     
       1. In a thermal head having a substrate, a heat accumulating member which is disposed on the substrate, a plurality of heating resistors which are juxtaposed on the heat accumulating member in a manner to be spaced from each other, a plurality of electrodes which supply electric power to the heating resistors, and a protective member which prevents oxidation and wear of the heating resistors and the electrodes; the thermal head being characterized in that said protective member comprises printing dot portions which are formed independently of each other above the respective heating resistors without a finite contacting area therebetween, which printing dot portions are made of thermally conductive members higher in thermal conductivity than the other part of said protective member, the surfaces of said thermally conductive members being even with a head surface formed by the portion of the protective member other than said printing dot portions. 
     
     
       2. A thermal head according to claim 1, wherein said thermally conductive member is disposed so as to be thermally joined to said heating resistor with one face thereof held in direct contact with said heating resistor. 
     
     
       3. A thermal head according to claim 1, wherein said thermally conductive member is disposed with an electrically insulating member interposed between one face thereof and said heating resistor. 
     
     
       4. A thermal head according to any one of claims 1 to 3, wherein a surface of said thermally conductive member on a side thereof at a surface of said printing dot portion differs in size from a surface on a side thereof at said heating resistor. 
     
     
       5. A thermal head according to claim 4, wherein the shape of the surface of said thermally conductive member on the side at the side surface of said printing dot portion is made smaller than the shape of the surface thereof on the side at said heating resistor. 
     
     
       6. A thermal head according to claim 5, wherein said thermally conductive member is so formed that a sectional shape thereof becomes smaller stepwise from the heating resistor side toward the printing dot portion surface side. 
     
     
       7. A thermal head according to claim 5, wherein said thermally conductive member is so formed that a sectional shape thereof becomes smaller continuously from the heating resistor side toward the printing dot portion surface side. 
     
     
       8. In a thermal head having a substrate, a heat accumulating member which is disposed on the substrate, a plurality of heating resistors which are juxtaposed on the heat accumulating member in a manner to be spaced from each other, a plurality of electrodes which supply electric power to the heating resistors, and a protective member which prevents oxidation and wear of the heating resistors and the electrodes; the thermal head being characterized in that said protective member comprises printing dot portions which are formed independently of each other above the respective resistors without a finite contacting area therebetween, which printing dot portions are made of thermally conductive members higher in thermal conductivity than the other part of said protective member, the surfaces of said thermally conductive members being even with a head surface formed by the portion of the protective member other than said printing dot portions, and a sealing member for shielding said heating resistors and said electrodes from external air. 
     
     
       9. A thermal head according to claim 8, wherein said sealing member is disposed so as to cover said electrodes and said heating resistors. 
     
     
       10. A thermal head according to claim 8, wherein said sealing member is disposed so as to cover said electrodes and said thermally conductive members. 
     
     
       11. A thermal head according to claim 8, wherein said sealing member is disposed so as to cover said protective member and said thermally conductive members. 
     
     
       12. A thermal head according to any one of claims 8 to 11, wherein said sealing member is made of an electrically insulating material. 
     
     
       13. A thermal head according to claim 8, wherein said thermally conductive member is disposed so as to be thermally joined to said heating resistor with one face thereof held in direct contact with said heating resistor. 
     
     
       14. A thermal head according to claim 8, wherein said thermally conductive member is disposed with an electrically insulating member interposed between one face thereof and said heating resistor. 
     
     
       15. A thermal head according to any one of claims 8, 9, 10, 11, 13 and 14, wherein a surface of said thermally conductive member on a side thereof at a surface of said printing dot portion differs in size from a surface on a side thereof at said heating resistor. 
     
     
       16. A thermal head according to claim 15, wherein the shape of the surface of said thermally conductive member on the side at the surface of said printing dot portion is made smaller than the shape of the surface thereof on the side at said heating resistor. 
     
     
       17. A thermal head according to claim 16, wherein said thermally conductive member is so formed that a sectional shape thereof becomes smaller stepwise from the heating resistor side toward the printing dot portion surface side. 
     
     
       18. A thermal head according to claim 16, wherein said thermally conductive member is so formed that a sectional shape thereof becomes smaller continuously from the heating resistor side toward the printing dot portion surface side.